Process for treatment of hydrocarbons



July 28, 1942. w. A. scHULzE PROCESS FOR TREATMENT OF HYDROCARBONS FiledMarch 20, 1939 2 Sheets-Sheet l INVENTOR WALTER A. SCHULTZE July 28,1942. w. A. scHuLzE PROCESS FOR TREATMENT OF HYDROCARBONS Filed March20, 1939A 2 Sheets-Sheet 2 Il wmOa ommE.

INVENTOR WALTER A. ySCHULZE A O EY Patented 1942 -nrnaocanaons ,minimumom., marilena' Felt@ a corporation of vinvention relates to'the'jtreatproved catalytic rn carbons. In 'afmore-specifl this invention is aprocess ottreating petroleum hydrocarbons such as thelower members oithe paraflin series (excepting methane), which occur in'crude petroleumoils, naturalfgasolines 'and Y natural gas,` inthe vapor form overcertain cat'- alytic materials v'to remove the -v organic sulfurcompounds and other desirablereining etIects. v, 'I'his application-'isacontinuation-in-'part foi' my copending application *Serial No`.vv196,691; tiledOctober 20, 1936; In I another copen'dir'ig application,'Serialv 'j No. 104,306, filed October'o, u1936,11 have shown the efectsobtained'fby"treatingfhydrocarbon vapors over catalytic "materials Yoithe buxiteftype at' temperatures of 900 to "1200" In addition' vto the'decomposition of organic sulfur impurities, other reactions are made totake place, vanion-g which are' "debydrogenation reactions. While thelexact nature of the reactions which *occur during the treatment ofiightfhydrocarbon's over acatalyst 'of thepeculiar nature of'bauidtehave' not been proven conclusively, it isfreasonably certainthat several concurrent reactions occur, namely (1) decomposition ordeleterious organic sulfur compounds to hydrogen sulde whi be removed,(2) decomposition and subs removal of impurities other than thesuli (3)-dehydrogenationof hydrocarbon c nts, and (4) changesin'molecularstructure oi; certain of the hydrocarbons, the-extent of .each reactionvarying with t and the convertive conditions.4 l i i I- havediscovered-certain improvements Vin catalytic materials Yfor effectingthese. changes which xnnt'otrhy# t drocarbons andrelates f moreparticularly to `im ethods of treating such hydro-v e c sense one the"obiects i@ wat to produce dehydrogenationapd.

. said :hydroxide:changed:v

, decomposing the`V object yst f orfsimulta-neously ionable yorganicvsulfur compounds ,and the like "and dehydrogenating certain j of s the4hydrocarbon" constituents i.: and changing vthe molecularvv structure of:certain utilized Las contact -catal t of invention, gnatedwith a solu-@In-thefspeciiic embodimen dehydrated bauxite is impre tion of yasoluble chromium. salt suchfasthe ni-` trate. The chromium salt'inratherconcentrated solution is merely sprayed as a-mist ontothe dehydrated.bauxite which completely adsorbsthe solution and immediately appearsdry. The subsequentconversion of said chromiumsaltzto'the oxide may-beaccomplished in several ways. For example, the nitrate may be reduced tothe oxide formbypassing hydrogen or other'reducing gas over theimpregnated bauxite at elevated tem-4 perature. 'On-'the nitrate may-belconverted by alkaline solution `treatment to'theihydroxide, and tooxid in a'stream'of a' reducing gas.v

.Heretofore` `certainrening' materials `have been made bymixing'certain' metal ysaltsy with nelyl 'divided or colloidal clay bydissolving-v the salts in av liquid solvent v andv adding the solutiontotheA clay tofform a gel, -rbutinsuch instances'. the-liquidand claywere rst stirred-into a paste,

. or cream, a'n'd thesolve'ntremoved later. Obvi` china? i equent, uronstitu-I'` he stock being treated.

result-ina remarkable' degree ofi-conversion with v only a smalldecreaseinvolumeofproductboil; ing-:within the` same rangeasthe untreatedstockst p f A further objectfoffthis, invention is --theiproduction oflarger quantities of hydrogen-during the treatment of hydrocarbon vaporsover. these improved catalytic materials, the increased quan-- tity ofhydrogen. being due to more hydrogenation of the hydrocarbons.

In its broader aspects, the invention lies i n.. the

peculiar combination of :a .highlycatalyticladsorbent material such asbauxite with a .metallic oxide which exerts a ,strong dehydrogenationach' tivity on hydrocarbons, which combination .is

extensive depounds are decomposed to. hy

' organic :sulfur compoun terial is far y*different ously my. process ofmanufacturing catalytic maf ,-fand due` to its-simplicity hasnianyfeconomic advantages. Furthermore,

I believe no mention has eve specic catalytic 'material-v com and achromiumsalt orvoxidei "It-haverdiscovered that -bauxi-te'f-impregnatedn `extremely effective( with chromium oxide' 'isl a catalytic materialfor deh carbons.v and'` simultaneo s uliur compounds to hy ognized thatchromium oxidehasdehydroge'nat ing-:properties vbut such catalysts Aare.generally very susceptible to poisoning, especially 4by `sulfurcompounds and the-like.`l` ItA is-known, too, that bauxite has excellentdesulfu'rizing activityv and ds suoliy as mercaptans, ke are decomposedto hy- 'Itis possible, therefore, to treat ngfhydrocarbon vapors in aninbauxite whereby the sulfur comdrogenA suliide, then e; andsubsequently ydrogenation of: hydrous conversion of f 'organicialkyl'suldes' and the li drogen .1 sulde: the sulfur beari itial stepwith remove..l the hydrogen suliid contact the desulfurized v va oxideLgelr whereby some" de hydrogenation ofthe hydrocarbons takes place.

I have found, .how-

drogenf'sulilde.:`r 'It is rece porsv over chromium' the use of bauxiteimpregnated with chromium oxide.

,I believerthe excellent results obtained with the bauxite-chromiumoxide catalyts are due to the fact that the chromium oxide in thismixture is not readily poisoned by the sulfur compounds in thehydrocarbon vapors. I have found that when treating sulfur-bearinghydrocarbon vapors over chromium oxide alone that considerable hydrogensulfide is taken up either by adsorption or by 1 conversion of the oxideto the sulfide. Similarly when treating such vapors over bauxite oraluminum oxide very little hydrogen sulfide is retained by the catalyst.I have concluded, therefore, that adsorption and desorption of hydrogensulfide from bauxite are both very rapid whereas dey sorption ofhydrogen sulde from chromium oxide gel is very slow. It is likely thatthe socalled poisoning of chromium oxide for dehydrogenation is due tothis slow desorption of ao cumulated hydrogen sulfide. The bauxiteimpregnated with chromium oxide constitutes a. catalytic mass whichdesorbs hydrogen sulfide at a very high rate; hence this catalyticmaterial is not Isusceptible to ordinary poisoning with sulfur compoundsand is highly effective for the purposes claimed. l

Instead of the bauxite-chromium lnitrate preparation, a Verysatisfactory catalytic material may be made by impregnating bauxite witha concentrated solution of ammonium dichromate. vThe material may thenbe heated to the temperature where the ammonium dichromate decomposesslowly to chromium oxide. Other soluble chromium salts readilyconvertible to the oxide form may, of course, be employed.

Diaspore and other naturally occurring baux"- ite1ike `materials may beused instead of the bauxite in the preparation of these improvedcatalytic materials. I have found moreover that certainv commercialaluminas, although Vmuch more expensive than bauxite, when used for thisPurpOSe frequently make much less. effective catalytic materials thanthe naturally occurring bauxites. I attribute this `difference to thephysical and chemical structure of thesey ma terials. It is fairlydenitely established that gibbsite is AlzOzHzO and diaspore isAlzOa.HzO, but the composition of bauxite is still doubtful..

.In utilizing catalysts of the present type in the treatment ofhydrocarbon vapors, they may be employed alone or in admixturewlthrelatively inert siliceous spacing materials.

Catalytic materials containing variousVV per centages of chromium oxidemay, of course, be prepared according to my invention. A verysatisfactory material consists l of 95. parts by Vweight bauxite and 5parts l'chromium oxide.

Smaller or larger percentages of chromium oxide may obviously be usedbut extremely economic. catalysts can be prepared through the use ofless than 5 per cent chromium oxide.

i It has been found that with use these catalysts gradually lose theiractivity due to the accumulation of carbonaceous residues, but they maybe reactivated indefinitely by burning out in situ with steam and air,or an oxidizing gas, or by burning in a furnace.

It is a feature of the present invention that when employing catalystsof the type disclosed that relatively low temperatures are sufllcient toproduce a marked reduction in sulfur content, as well as substantialdehydrogenation of normally lconditions warrant them. In practice,however.

it is usually` desirable to use pressures somewhat above atmospheric sothat the vapors may be conducted directly to a fractionator or totreating. tanks for nal processing. The preferred flow rate is of theorder of 1 to 10 liquid volumes of feed stock per hour per volume ofcatalyst.. At the higher temperature levels shorter contact times aresufficient; therefore, flow rates as high as liquid volumes per hour pervolume of catalyst may be employed. i

Numerous examples might be given of the effects obtained by usingtheparticular catalytic materials comprised within the scope of theinvention in the treatment of light parai'iin hydrocarbons, but thefollowing is sufficiently indicative of the improved results which wereobtained.

Example I l K v Anuntreated butane stock consisting substantially ofnormal butane obtained from a Mid-V Y the hydrogen contentof the treatedgas to vary Abetween 22.0 and 23.5 per. cent by volume,V while the totalunsaturation of said gas varied between 15.4 and 16.5 per cent. i

A composite `sample representing the entire run was collected and thefollowing analysis was obtained:

Volume per cent The unsatura'tion of this sample was 15.45 per cent,indicating somewhat larger unsaturation than -is represented by thetotal per cent of unsaturated C4 hydrocarbons which in this case was14.5 per cent. This increase in unsaturation is accounted for bydehydrogenation of the minor amounts of propane and ethane resultingfrom the convertive reactions. It should also be noted that unsaturatedhydrocarbons include 3.25 per cent by volume of isobutylene resultingfrom arearrangement or isomerization reaction on the catalyst.

The emuent gas from the catalyst was found to be substantially free oforganic sulfuriimpurif ties present in the raw material, indicatingsub-- 4stantial decomposition ofsaid organic sulfur compounds by thedesulfurizing action of the catalyst.

The fixed gas calculated as ethane and lighter" formed during thetreatment of this normal butane amounted to about 600 cubit feet (S. T.,P.) per barrel of butane charged. Of this ilxed` gas, hydrogen gasamounted to about 88 per centl by volume and methane to about 6` percent by volume or a hydrogen/methane ratio of about 14.5. At the end ofabout 12 hours, the catalyst showed some evidence of decline in activitydue to carbon formation, but its activity was completely restored byheating and burning outr with air.

" Y Example II passed in vapor form over a catalyst com- The same normalbutane of Example I was posed of 95 parts by weight bauxite impregnatedwith` 5 parts by weight chromium oxide at a-temperature 'of 1070 F.,atmospheric pressure and a ilow rate of 2.5 liquid volumes of butane perhour per volume of catalyst. At the higher ow rates the fixed gasevolved amounted to only about 300 cubic feet (S. T. P.) per barrelofbutane charged. An incomplete analysis of this total eilluent gas was asfollows: Y

Volume Ga? per cent H'. 21. 5 CH; 1. 5 CQH.. 0. 7 02H6 0. 6 C; andheavier 76. 7

The unsaturation of the treated vaporsaveraged about 14.5 per centduring a 24 hour run, indicating about l5 per cent conversion per massof the normal butane during' this operating cycle. The hydrogen/methaneratio in this case was about 14.

' Example III Propane may be passed in the vapor form over thebauxite-chromium oxide catalyst at a temperature ranging between 1060and 1100 F. and a flow rate corresponding to one liquid volume ofpropane per hour per volume of catalyst space.

. The conversion of propane during a period of 10 hours averages aboutpercent. The sulfur compounds in the propane are decomposed to `hydrogensulfide.

Example IV A light hydrocarbon gas containing 12 percent ethane, 23 percent propane, 30 per cent isobutane and per cent normal butane may bepassed in the vapor form at temperatures in the range of 1000 to 1100 F.over bauxite impregnated with chromium oxide. When the temperature ismaintained near 1000" F. and the ow rate corresponds to two liquidvolumes per -hour per volumeof catalyst space, the normal 'hydrogenatedIn each instance the sulfur compounds are decomposed to hydrogensulfide. Recycling of part of the stream of hot treated vapors for asecond pass through the catalyst tower increases the extent ofconversion still further.

l I have found that in the treatmentfof low molecular weight normallygaseous paramn hydrocarbons over these bauxite catalystsimpregnatediwith chromium oxide in the temperature range of- 800 to 1100F., as lshown in the examples given above, considerable dehydrogenati nof the hydrocarbons occurs as well as some isomerization. -i ThereA isonly a: very slight amount of cracking, as evidenced by the smallproportion of methane in the gas, providing, of

course, that the temperature and contact time In the practice of myprocess 'for the treatment-of hydrocarbon stocks toobtain'desulfurization, dehydrogenation and the like concurrently, bestresults are obtained with vrather thoroughly dehydrated catalyticmaterials; The

ilrst'step in this process usually consists, vtherefore,

oxide catalyst, preferably in situ, by raising the temperature graduallyto the temperature of op-1l erationor higher while a slowstream ofY airor! hydrocarbongas is passedoverit. Vacuum drying may be done, ifdesired. This step of passing air or hydrocarbon gas over the catalystcan obviously be omitted in practice, and the hydrocarbon-vapors startedimmediately over the catalyst. Much of the improvement'normally obtainedin the hydrocarbon stock will vbe lost, of course, during the iirst fewhours of operation in Athis manner, or atleast until the workingtemperature has been reached and the catalyst has been substantiallydehydrated.

It has been found that the hydrogen-bearing gas which is formed duringthe treatment lof hydrocarbonv stocks accordingto my-invention may berecycled through the system by' adding such gas, or a portion of it,tothe hydrocarbon vapors prior to passage over the catalyst.- Suchhydrogen gas should, of course, not be allowed' methods forthe-removalof the small amounts of hydrocarbons higher than methane vConcentrations of hydrogen Vhigher than 95 per cent can be obtained bymore elaborate extraction genation and/or other purposes can be obtainedin this treatment of gasoline stocks over bauxitechromium oxide catalystat .extremely low cost.

A vvery distinct advantage of my process isthe formation ofrelativelylarge quantities of lhydrogen from such hydrocarbonsms thoseof the aliphatic `series with` methane being Vthe only impurity inappreciable amount. Obviously this gas can be utilized for many purposeswhere the in dehydrating the bauxite-chromium-I more common mixture 'ofhydrogen and carbon monoxide cannot .be tolerated at any -cost.

I: desired, the hydrocarbon vapors-,may, be

given two or more successive treatments withthe `bauxite-chromium oxidecatalyst in a series oi towers, or the vapors or any fraction thereofmayA be. recycled with the fresh vapors through the.

catalyst tower. Some additional heat, also, may be supplied to thevapors prior to thesecond and/or successive catalytic treatments.

Following the treatmentof theyapors over the catalyst the decomposedimpurities and light gas fraction are separated from the heavierhydrocarbons by fractional condensation oriany othervconventional'means, as will be well understood by those skilled in theart.4 If desired, the uncondensed light gas fraction may be passedvthrough avapor recovery p lant of the-.absorption or other conventionaltype lwhereby the hydrocarbons otherthan methane may be recovered andmade useful for other purposes.v Also, the

decomposed impurities may be removed -by ,chemical means in a step apartfrom that of removalof the hydrogen and methane.v 'i

The low-boiling -parailin hydrocarbon betreated in any manner vsuitablefor removing or vutilizing vthe unsaturates contained therein,

such asf polymerization of propylene andbutylenes to form polymergasoline. After such treat-.

ment, the unchanged paraflnichydrocarbons maybe recharged to my catalystfor further con-i version andfdehydrogenation.

Any methane occurring withsaid law stocks.

or formed during the catalytic conversion may be treated along with theheavier hydrocarbons,

said methane gas being. substantially unchanged at conversion conditionsand acting merelyasa diluent-.and a source of vheat for the reactantFigure lgrepresents schematically one type yo f apparatus in whichmy-process maybe `used. This drawing shows the-raw.hydrocarbonvstockvapors entering a 'heater l where they areraised to the desired treatingtemperature. Fromthe heater the :hot vapors pass directly to thecatalyst chamber 2,-- and afterpassage overthe catab'st,

maygo direct to the fractionating unit 4, or may be treated for-,theremovalof hydrogen sulde at f3. In the fractionating unit the treatedvapors are fractionated to send thehydrogen and light--V er hydrocarbonsover vheaciwhile theheavierhyd d rocarbons pass to the unit SV ,forextraction ofr olefins; Said heavier hydrocarbons may alternatively betreated for hydrogen sulfide removal at 8, prior 4to unit 5. From 5 theunconverted parailin hydrocarbons may be returned through therecycle-line to thecompressor 1 and -thence tothe heater `l for heatingprior' to:` a second catalytic treatment. Also, all or axportion of thehydrogen and lighter hydrocarbon fraction stocksaiter treatmentaccording to this invention may asentar' edraw hydrocarbon vapors priorto'passage.into',-v the catalyst tower. Figure 3 illustrates .analternative .methodfor living hiirotiar'bcnv vapors successive treatmentsin-two `catalyst towersin series with the alternative also of `recycling.,a portion of the hot trea ted vapors.A Figure 4 illus,-v

trates@ method ior supplying additional vrheat to the hydrocarbon stock-Vvapors prior to vthe -second catalyst tower. y 'I'heforegoingspecinc'ation and exampleshave disclosed and illustrated theinvention, butsince it is of generally -wideapplicatipn and the numberof examples of results obtainable by vits'use might be multiplied`greatly. n `either is to be construed as imposing limitations upon thescope of the invention. The term light or low-boiling paramnhydrocarbons as used hereinv includes the normally V'gaseoushydrocarbons of' 'the aliphatic series containing two to four carbonatoms such may be sent through compressor 1 and recycled` Y vtherecyclingas occur inv natural gas,' 'naturalf gasolinas." re-l nnerygases and vaporrecovery gasolinesr and polymerizationprocesses and/or`mixtures' or blends ffnytwo-or more of said light '-paraiiinhydrocarbons.' f' 25 Iclaim:

1. A process for concurrently desulturizingand dehydrogenating organicsulfur-'containing ali'' phatic hydrocarbon stocks containing two tofour carbon` atoms which comprises contacting said hydrocarbonstocks invapor form at pressures between atmospheric and pounds per square inchwith a dehydrated bauxite catalyst impreg` nated with a solution of achromium compound; vsubsequently converted to chromium oxide, the

catalyst, containing a major proportion of bauxite and a .minorproportionof chromiumoxide,` at a temperatureywithin the ran8e of 800 to11009A F; L'and'a;f1ow.. rate,of about l tov- 1Q liquid volumes ofraw-material per hour pervolume of catalyst..

dividing the eiiluent from the catalyst treatment into two streamsof-identical composition, recycling one of the streams withoutsubstantial cooling back into" the raw heated vaporsprior -to the'catalyst chamber, separating'froni the other stream'of treated vaporsthe decomposed iin-' purities vand the gas fraction containing asub'vstantial' proportion of' hydrogen gas, 'and the heavierhydrocarbons, and4'thereby obtainingv substantially! de sulfurized vhydrocarbon stockswithy greatly increased unsaturation;

2. A process for dehydrogenating aliphatic hydrocarbon stockscontainingtwo to tour carbon atomsvlwhich comprises contactingrsaidhydrocarbonstoclc's .in vapor" form atpr'essurejs' between atmosphericand 100 pounds per square inch with a dehydrated bauxitelcatanaitimpregnated with a solutionof a chromium compound subsequent'-ly converted tochromium oxide,',the"dehydrat`ed catalyst containing amajor proportion ofba'uxite and a minor proportion o'f chromium oxide;at a temperature in the range of 4800fto 11 0O F. and

a new rate of about 1 to 1o nquid'volumes of nyy drocarbon :stocks perhour pervolume of catalyf's't.,` dividing the eiluent from the catalysttreatment into two streams of identical composition`,. re-

cyclingone of the streams without substantial cooling back into the raw.heated vapors prior to the catalyst chamber and 'separating theotherstream of treated lvapors inta `vlight fraction consisting mostlyofhydrogenand ahydrocarbonstock of greatly increased unsaturation. WALTERA. SCHULZE.

